Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h, w = map(int, input().split())
bord = [list(input()) for _ in range(h)]
visit = [[-1 for _ in range(w)] for _ in range(h)]
visit[0][0] = 1


q = deque([[0,0]])
visit[0][0] = 1
while q:
    px, py = q.popleft()
    for i, j in ([1,0],[-1,0],[0,1],[0,-1]):
        if px+i >= 0 and px+i < h and py+j >= 0 and py+j < w:
            if bord[px+i][py+j] == "." and visit[px+i][py+j] < 0:
                visit[px+i][py+j] = visit[px][py]+1
                q.append([px+i, py+j])
if visit[h-1][w-1] < 0:
    print(-1)
else:
    c = [i.count(".") for i in bord]
    print(sum(c)-visit[h-1][w-1])